The present invention refers to a fastening sleeve for fastening different machine members such as bearings or gear wheels to a shaft.
Different devices for fastening of machine members to a shaft are earlier known. Such devices, which are made of steel, can be expansion sleeves, members incorporating wedge grooves, tapering fastening sleeves and the like. A conventional method of fastening e.g. a bearing to a shaft is to provide the bearing with a tapering bore and to use a tapering fastening sleeve, upon which the bearing is driven up by means of a nut which is locked after the driving up operation is completed. Such a sleeve provides a reliable connection but it requires a tapering bore in the bearing and it is also necessary to manufacture both sleeve and bearing with the utmost accuracy. This means that the sleeve will be very expensive and almost as expensive as the bearing itself. Another very big drawback in the use of fastening sleeves of steel is their big tendency of causing "fretting corrosion" which sometimes can occur after a very short time of use. It has, therefore, since long been strongly desired to be able to provide a fastening member of a less expensive type, which will still provide the same or even a better fastening function than the mentioned steel sleeve.
These problems have according to the invention been solved by providing a fastening sleeve, which incorporates a slotted body of pressed sheet metal, which is embedded in a plastic material or the like whereby one surface of the sleeve is tapering and one axial end of the body is free from the moulding compound.
The sheet metal body of the fastening sleeve is primarily intended as a good reinforcement for the plastic material moulded thereabout, but it has thereabove as a primary task to transfer and distribute the forces, which are required for the axial displacement of the fastening sleeve at assembly and dismounting respectively. One axial end surface of the sheet metal body shall hereby be free from the plastic material moulded thereabout since the end surface which forms a stop at the mounting must necessarily be purely metallic for being able to withstand the pressure load, which will occur. It is appropriate that the sheet metal body when embedded in plastic is centered in the moulding tool at its pure metallic end surface and thereabove by means of projections on sheet metal tongues, which are stamped in the sheet metal and which support and center the sheet metal body against the central mandrel of the moulding tool as well as against its outer parts. Besides its centering function during the moulding process these supporting elements form desirable friction spots after the assembly of the fastening sleeve.
In order to increase the adherance between the sheet metal body and the plastic the sheet metal body is provided with perforations. During the moulding process these perforations act thereabove as pressure compensating channels between the two envelope surfaces of the thin sheet metal body.
At perforation of the sheet metal body it is possible to allow sheet metal lugs at least at some of the breaking through points to be designed to form stops at the moulding operations or friction points after the assembly. The plastic compound in which the sheet metal body is embedded will give the fastening sleeve its shape and its tolerance zone. The assembly force used against the sheet metal body is transferred via the plastic compound to pressure and friction forces, which are adapted to the function for which the fastening sleeve is intended.
One of the envelope surfaces of the fastening sleeve, either the inner one or the outer one is always made tapering whereas the sleeve in the axial direction is slotted in order to allow the expansion which is aimed at during the mounting of the sleeve.
At one of its axial ends the sheet metal body can be provided with threads, a mounting ring or the like or one end of the sheet metal body can alternatively project outside the embedment and there form a stop. At fastening of machine members having tapering center bores, e.g. ball bearings with tapering centre bores, only one fastening sleeve is used the outer envelope surface of which is tapering.
When fastening machine members having cylindrical central bores two fastening sleeves are used, the tapering envelope surfaces of which are adapted for being driven up against each other.
A common advantage at the use of fastening sleeves according to any embodiment of the invention is that the sleeves cannot give rise to fretting corrosion which is very important.